Field of the Invention
This invention relates to a recording technology using a plurality of recording devices.
Description of the Related Art
Recording using an IC recorder may be performed at a small-scale concert such as a recital of a music class. Such recording is performed in a state where the microphone of the IC recorder disposed at auditorium seats is directed toward the performer on the stage. At this time, a zoom function having directionality is used such that only the performer's performance is clearly recorded.
However, it is difficult to obtain perfect directivity with the microphone built in the IC recorder. For example, noise such as sound that an audience makes when opening a brochure or sound of cough may be mixed in the desired audio. Therefore, it is difficult to obtain a good recording result.
The principle of a general directional microphone will be described. The directional microphone is configured with a plurality of microphones. The plurality of microphones are arranged to be directed toward the direction of an audio source that generates audio to be recorded and its opposite direction, respectively. Audio other than audio from the sound source is canceled, by inverting the phase of audio from the direction opposite to the sound source direction, and superimposing the audio on audio from the direction of the sound source.
In order to further improve the directivity of the microphone, advanced design considering the propagation characteristics of sound waves and the like is required. It is difficult to obtain high performance unless each microphone is disposed in an appropriate position. Therefore, the degree of freedom in design such as the size and shape of a device and the arrangement of respective microphones is limited. Due to these conditions, the cost of design and manufacturing to obtain high directivity is high. Therefore, in general, a directional microphone function with high performance is mounted in a professional IC recorder used for a specific application. On the other hand, a general-purpose IC recorder used by users other than professional users is equipped with a directional microphone function called a zoom microphone. However, in order to maintain the balance between cost, versatility, convenience of carrying and the like, a microphone which obtains high directivity is not mounted.
Japanese Unexamined Patent Application Publication No. 2013-78118 discloses a method of reducing a noise component included in an audio signal. In the method disclosed in Japanese Unexamined Patent Application Publication No. 2013-78118, a main audio microphone and a reference microphone that collects noise are determined by using a phase difference between audio signals obtained by a plurality of microphones provided in a device.